Impromptu Metal Detector Built From The Junk Bin

August 30, 2021 by Tom Nardi 12 Comments

Have you ever found yourself suddenly in need of finding a small metal object hidden in the woods? No? Well, neither have we. But we can’t say the same thing for [zaphod], who’s family was hoping to settle a dispute by finding the surveyor stakes that marked the corners of their property. It was a perfect job for a metal detector, but since they didn’t own one, a serviceable unit had to be assembled from literal garbage.

To start with, [zaphod] had to research how a metal detector actually works. After reviewing the pros and cons of various approaches, the decision was made to go with a beat frequency oscillator (BFO) circuit. It’s not the greatest design, it might even be the worst, but it could be built with the parts on hand and sometimes that’s all that matters. After packing a 2N3904 transistor, an LM386 amplifier, and every Hackaday reader’s favorite chip the 555 timer into an enclosure along with some of their closest friends, it was time to build the rest of the metal detector.

The sensor coil was made by salvaging the wire from an old fluorescent lamp ballast and winding it around the lid of a bucket 27 times. This was mounted to the end of a broom handle with some angle pieces made from PVC sheet material, being careful not to use any metal fasteners that would throw off the detector. With the handle of an old drill in the middle to hold onto, the metal detector was complete and actually looked the part.

So did [zaphod] save the day by finding the surveyor stakes and reconnoitering the family’s plot? Unfortunately, no. It wasn’t a technical failure though; the metal detector did appear to work, although it took a pretty sizable object to set it off. The real problem was that, after looking more closely into it, the surveyors only put down one stake unless they are specifically instructed otherwise. Since they already knew where that one was…

If your homemade metal detector can’t find something that was never there, did it really fail? Just a little something to meditate on. In any event, when even the cheapest smart bulb is packing a microcontroller powerful enough to emulate early home computers, we’re always happy to see somebody keep the old ways alive with a handful of ICs.

Circuit Sculpture Vibration Sensor

January 10, 2021 by Kristina Panos 15 Comments

Here’s your useful and beautiful circuit for the day — [New Pew]’s vibration sensor takes manual control of the flip-flop inside a 555 timer and lights an LED in response. Use it to detect those vibrations you expect, like laundry machines, or those you only suspect, like the kind that might be coming from your engine. This gadget isn’t super-precise, but it will probably get the job done.

The vibration-detecting bit is a tiny ball bearing soldered to the spring from an old pen, which is tied between the trigger and ground pins of the 555. When the chip is powered with a 9 V battery, nearby vibrations will induce wiggle in the spring, causing the ball bearing to contact the brass rod and completing the circuit. When this happens, the internal flip flop’s output goes high, which turns on the LED. Then the flip flop must be reset with a momentary button. Check out the build video after the break.

Want to pick up Earthly vibrations? You can detect earthquakes with a homemade variable capacitor, a 555, and a Raspberry Pi.

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Killing Mosquitoes With Cardi B

December 5, 2020 by Bryan Cockfield 31 Comments

Keeping a bird bath or a pond in your yard is a great way to add ambiance and style, but both of these things can be a haven for mosquitoes. Popular methods of getting rid of them are often with harsh pesticides, but [Shane] has brought us a more environmentally-friendly way of taking care of these disease-carrying insects by looping a Cardi B playlist underwater, killing the mosquito larvae.

While the build does include some other favorites such as “Baby Shark” and would probably work with any song (or audio of sufficient volume) the build is still pretty interesting. It’s based on a 555 timer circuit which powered an ultrasonic sound gun, but was repurposed for this build. The ultrasonic modules were replaced with piezo modules which were waterproofed with silicone. The sound produced vibrates at a frequency which resonates with the mosquito larvae and is fatal to them. [Shane] put the build into a small boat which can be floated in any pond, bird bath, horse trough, or water feature.

The major caveat to this build is that it may be damaging to other beneficial animals such as fish or frogs, so he suggests limiting its use to uninhabited stagnant water. Either way, though, it’s a pretty unique way of taking care of a mosquito problem not unlike another build which takes care of these insects in water a slightly different way.

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Teardown: Mini GPS Jammer

September 8, 2020 by Tom Nardi 142 Comments

If you spend enough time trolling eBay for interesting electronic devices to take apart, you’re bound to start seeing suggestions for some questionable gadgets. Which is how I recently became aware of these tiny GPS jammers that plug directly into an automotive 12 V outlet. Shipped to your door for under $10 USD, it seemed like a perfect device to rip open in the name of science.

Now, you might be wondering what legitimate uses such a device might have. Well, as far as I’m aware, there aren’t any. The only reason you’d want to jam GPS signals in and around a vehicle is if you’re trying to get away with something you shouldn’t be doing. Maybe you’re out driving a tracked company car and want to enjoy a quick two hour nap in a parking lot, or perhaps you’re looking to disable the integrated GPS on the car you just stole long enough for you to take it to the chop shop. You know, as one does.

But we won’t dwell on the potentially nefarious reasons that this device exists. Hackers have never been too choosy about the devices they investigate and experiment with, and there’s no reason we should start now. Instead, let’s take this piece of gray-area hardware for a test drive and see what makes it tick.

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Pocket-sized Device Sniffs Out Damp Masks

September 6, 2020 by Tom Nardi 13 Comments

The realities of wearing a mask when you go out, from forgetting the thing in the car to dealing with fogged up glasses, have certainly taken some getting used to for most of us. But not every issue is immediately obvious. For example, experts say that as a mask gets damp from exhalation or perspiration it becomes less effective. Which is precisely why [Rick Pannen] has designed the Mask Moisture Meter.

As deep as we are into the Microcontroller Era, we really appreciate the simplicity of this design. It’s just a 555 timer, a buzzer, some LEDs, and a handful of passive components to get them all talking to each other. There’s no firmware or programming required; just put a fresh battery in the holder and away you go. The traces of the PCB serve as a moisture detector, so when the board is pushed against something wet enough, the red LED and buzzer will go off to warn the user.

Now admittedly, there’s a point where you certainly won’t need an electronic gizmo to tell you a mask is wet. But as [Rick] demonstrates in the video after the break, the circuit is sensitive enough to indicate when there’s moisture in the material that might not be immediately obvious to the eye.

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A Shrine For All The 555 Lovers

July 15, 2020 by Sven Gregori 26 Comments

For many of our readers, the classic 555 timer holds a special place in their heart, and cursed be the fool who dares to use an Arduino in its place. For the seriously devoted ones, or those who simply like a novelty decorative item, [acerlaguinto7] built just the right thing: a giant, actually functional, cardboard 555 timer IC.

Taking all the measurements of the original IC, [acerlaguinto7] scaled it up by factor 22 and started cutting out pieces of cardboard — also considering the orientation notch — and added the markings to emulate TI’s NE555P. Next he took a bunch of aluminum cans apart and shaped them into the pins, again staying as close as possible to the original. To top it all off, he put an actual NE555 inside the giant counterpart, and hooked it up to the soda can pins, turning it into a fully operational, oversized timer IC.

Obviously, giant conductive pins like that scream for some dead bug blinky light that even the shakiest of hands could manage to solder, and [acerlaguinto7] certainly delivers, as you can see in the video after the break. One nifty way we could see this taken further would be integrating this breadboard implementation as replacement for the 555 inside — or then just connect it to the giant Raspberry Pi.

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Dub Siren Synth Does It The Old School Way

November 29, 2019 by Lewin Day 18 Comments

There’s little that can compare to the sheer obnoxious thrill of mashing the DJ siren when its your turn behind the decks. We’ve certainly been guilty of abusing the privilege at local house parties, and unsurprisingly have not been invited back. If we ever get another shot, though, we’d be glad to have [lonesoulsurfer]’s dub siren at the ready.

This is a build for the old-school purists. There’s no microcontrollers or digital hardware here. The synth relies on two 555 timer ICs as the oscillators and an LM741 op-amp. These parts harken right back to the dawn of the integrated circuit era, and still do a great job in this application. There’s also a cheap reverb/echo module added in to fatten up the sound. It’s all laced up in an old CB radio enclosure, with the classic woodgrain applique doing much to add to the aesthetic.

It’s a build that’s simple enough for the electronics beginner, and would make a great tactile, analog addition to any DJ’s rig. If you need some wubwubs to go with your woowoos, then consider building a Ball of Dub, too.

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